If you watch the hospital room when Jin gets there, it's a different woman who they give the panda to. Plus they said the baby was a boy when we know that Sun had a girl. It was definitely a FB for Jin and a FF for Sun.

I'm new to the board but I've been watching Lost since first day it aired. Although I hate to admit it, I think Jin is dead. Sun didn't cry at the graveyard like she left her husband behind on the island. She was crying like her husband was really dead.